1. Field of the Invention
This invention relates to physiological pressure sensing systems, and in particular to such a system utilizing a disposable pressure transducer.
2. Description of the Background Art
An improved flow control apparatus for use in liquid flow systems, such as for monitoring of blood pressure in humans and other animals, is disclosed in U.S. Pat. No. 4,291,702, of James E. Cole et al, which patent is owned by the assignee hereof. As disclosed therein, the flow control apparatus is adapted for use with fluid flow catheters, such as used in invasive connection as by insertion into a patient's blood vessel. In normal use in such systems, the catheter is provided with a sterile isotonic solution which is caused to flow through the catheter into the patient at a low flow rate sufficient to maintain the catheter open and unclogged as by blood cells and the like at the inserted end of the catheter.
As further pointed out in the Cole et al patent, the catheter system is firstly flushed of air before insertion of the catheter into the patient. To permit the system to be rapidly filled with the sterile solution which is used to flush the system of air, the catheter flushing apparatus of said patent further is arranged to selectively permit a high flow rate of the solution from the source to the catheter.
In one embodiment of the structure disclosed in the Cole et al patent, a flexible diaphragm is extended across an opening to the pressure chamber of the housing of the apparatus. Means are provided for connecting a fluid actuated transducer to the housing so that deflections of the diaphragm cause corresponding fluid pressure transmissions to the transducer.
A problem has arisen in the use of such systems relative to the high expense and unreliability of the pressure transducers before employed in such systems. Such transducers have been quite expensive in order to provide the necessary accuracy. As the transducers must be cleaned and sterilized from time to time, the useful life thereof has been relatively short. Such transducers further have been found to become inoperative as a result of the cleaning and sterilization processes. Such inoperativeness presents a particularly vexatious problem in that it normally occurs at the critical time of setting up the system with the patient as testing of the apparatus is normally conducted prior to the cleaning and sterilization steps because of the impracticality of testing subsequent thereto.
Further, the use of the reusable pressure transducers may cause cross-contamination and spreading of infection where complete cleaning and sterilization are not achieved.